Fas and TNFR1 expressions after cerebral ischemia and reperfusion in rats: association with cell apoptosis and the effects of Bcl-2 overexpression / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the effect of Bcl-2 overexpression on Fas and TNFR1-mediated apoptosis and its possible mechanism in rat hippocampus following global ischemia/reperfusion (IR).</p><p><b>METHODS</b>Ninety healthy male SD rats were randomly divided into sham operated group, IR group and Bcl-2 overexpression group (BT group). Rat model of global IR was established by the 4-V0 method. The expressions of Bcl-2, Fas and TNFR1 and the cell apoptosis in the CA1 and CA3 regions were examined by HE staining, immunohistochemistry and TUNEL method.</p><p><b>RESULTS</b>In IR group, the neurons in the CA1 region showed an obvious reduction in number with disordered arrangement and interstitial edema 48 h after global IR. Such changes were not obvious in BT group. Immunohistochemistry showed that Fas expression in the CA1 region reached the peak level at 6 h in IR group with a greater expression intensity than that in BT group (P<0.05). TNFR1 was expressed at a higher level in IR group than in BT group (P<0.05), reaching the peak level at 24 h. In the sham group, the expression of Fas and TNFR1 was not detected the in CA1 and CA3 regions. Global IR caused increased cell apoptosis in the CA1 and CA3 regions, starting at 6 h and reached peak at 24 to 48 h. The cell apoptosis was less obvious in BT group (P<0.05).</p><p><b>CONCLUSION</b>Fas and TNFR1 are expressed in the CA1 and CA3 regions after global IR in rats, suggesting the involvement of death receptor in cerebral IR injury. Bcl-2 overexpression decreases the expression of Fas and TNFR1 and cell apoptosis after global IR, thus offering protective effect against cerebral IR injury.</p>

Relationship between transmembrane signal transduction pathway and DNA repair and the mechanism after global cerebral ischemia-reperfusion in rats / 神经科学通报·英文版

<p><b>OBJECTIVE</b>To investigate the protein levels of phospho-ERK and phospho-APE/Ref-1 in hippocampal neurons after global cerebral ischemia reperfusion in rats, and observe the relationship between transmembrane signal transduction and repair of DNA damage. The role of ERK signal transduction pathway following global cerebral ischemia reperfusion in rats is further discussed.</p><p><b>METHODS</b>Ninety healthy male SD rats were divided into 3 groups randomly: Sham group (S group), Ischemia reperfusion group (IR group) and Pd98059 pretreatment/ischemia reperfusion group (PD group). Global cerebral ischemia reperfusion model was established by four-vessel occlusion (4-VO) method, and reperfusion was performed 5 minutes following ischemia. Protein levels of phospho-ERK and phospho-APE/Ref-1 were detected using immunohistochemical method at 2 h, 6 h, 12 h, 24 h, 48 h and 72 h after reperfusion, and neuron apoptosis was observed by HE and TUNEL staining.</p><p><b>RESULTS</b>In CA1 region of IR group, TUNEL positive cells began to appear at 6 h after IR, and reached the apex during 24 h to 48 h. However, TUNEL positive was most strongly exhibited in PD group. In IR group, phospho-ERK was obviously detected in CA3 region at 2 h after IR, and its level was gradually decreased from 6 h until totally absent at 48 h. Besides, phospho-ERK expression in PD group was weaker than that in IR group. For phospho-APE/Ref-1, its expression began to appear in CA1 region in IR group at 2 h after IR, with no obvious changes during 2 h to 12 h. Phospho-APE/Ref-1 expression began to decrease at 24 h and this decrease continued thereafter. Expression level of phospho-APE/Ref-1 in PD group was lower than that in IR group. Results showed the concurrence of decreased phospho-ERK expression level and increased neuron apoptosis after cerebral ischemia reperfusion, the former of which was consistent with the decrease of phospho-APE/Ref-1 expression. Also, the greater the inhibition of ERK phosphorylation was, the greater decrease of APE/Ref-1 expression occurred.</p><p><b>CONCLUSION</b>Activation of ERK signal transduction pathway increased the expression of phospho-APE/Ref-1, and thus faciliated the repair of DNA damage. So, activation of ERK signal transduction pathway may protect neurons from apoptosis after cerebral ischemia reperfusion.</p>